The natural diseases of New Zealand Black mice and their hybrids with the New Zealand White strain are under study by genetic, immunologic, and virologic procedures. These diseases comprise immune- complex glomerulonephritis, a model of human lupus glomerulonephritis; autoimmune hemolytic anemia, a model of human disease; and malignant lymphoma or leukemia. The natural history of the murine disease is characterized by endogenous C-type virus antigenemia, pathogenetic antibody responses both to endogenous C-type viral antigens and to self antigens, thymus and thymus-dependent lymphocyte (T-cell) deficiency, and development of the mentioned diseases, which are either mediated by, or involve, the immune system. The objective of the project is to probe and define the genetic, virological, and immunological determinants of these murini diseases, and to gain insight into the nature of corresponding human diseases.